1. Field of the Invention
The present invention relates to a recording apparatus capable of driving a recording head consisting of plural recording elements by time-division drive.
2. Related Background Art
With the recent commercialization of the information processing equipment such as copying machines, word processors and computers, and other communication equipment, digital image recording apparatus such as those employing a recording system or thermal transfer recording system are rapidly becoming popular for image output for the above-mentioned equipment. Such recording apparatus generally employs a recording head consisting of an array of plural recording elements (hereinafter after called multi-element head) for the purpose of increasing the recording speed. For example, in the ink jet recording, there is generally employed a so-called multi-nozzle head in which a plurality of ink discharge openings 100 and ink channels are integrally formed, and in the thermal or thermal transfer recording head, there are generally integrated plural heater elements.
For such multi-nozzle head, there is usually employed time-division driving method by dividing said head into plural blocks. Since the divided blocks are driven at different timings and the recording head performs scanning motion even between such different timings, there is generated a slight aberration in the position of recording. For compensating such aberration, the recording head is inclined as shown in FIG. 1.
Because of such inclined positioning of the head 30, the positions of the prints are aligned linearly, though the recording operations of the neighboring blocks are different by t.sub.b in time.
It is also possible to activate arbitrary ones among plural blocks of the recording head, as shown in FIGS. 2(A) and 2(B), which illustrate, as an example, the procedure of recording an input image in a size reduced to 1/2. At first blocks (digits) 9 to 16 (cf. FIG. 4) are blocked, and digits 1 to 8 are activated to record a 1/2-reduced image with the upper half of the recording head and with the main scanning motion (FIG. 2(A)). Then the digits 1 to 8 are blocked, while the digits 9 to 16 are activated to record a next 1/2-reduced image with the lower half of the recording head, with the main scanning motion but without the sub scanning motion (FIG. 2(B)).
In this example, each digit consists of 8 pixels or dots, so that the recording head can record 16.times.8=128 dots at a time.
A reduced print image shown in FIG. 2(B) can be obtained in this manner. Although satisfactory image quality can be obtained in the unreduced image, the image quality is deteriorated in the reduced image recording since the recording of the second line becomes aberrated from that of the first line, as shown in FIG. 2(b). Said aberration in the reduced image recording results from an aberration in the on-timing of the digits, as will be explained in the following with reference to FIGS. 3 and 4.
FIG. 4 shows the on-timing of the digits of the ink jet recording head at unreduced image recording. In every line, the digits are turned on sequentially from digit 1 to 16, in synchronization with basic clock signals. The on-timing of the digits in the reduced image recording is same as that of the unreduced image recording for the upper half (cf. FIG. 2(A)), but is different from that for the lower half (FIG. 2(B)). FIG. 3 shows the on-timing of the digits 9 to 16, wherein (a) and (b) respectively show the timing in reduced image recording and in unreduced image recording. It will be understood that the timing for each digit is different by a time Ta for these two recording modes.
The conventional driving method, as explained in the foregoing, has resulted in an aberration in the obtained print, since the drive timing is not changed according to the change in the sequence of time-division drive.